Real Dictionary

double
A double bed is a bed that is wide enough for two people to sleep in.
A double room is a room intended for two people, usually a couple, to stay or live in.
a method used to determine the location of antibodies or antigens in which the antibodies or antigens are labelled with a fluorescent dye [...]
a shore or beach [...]
Double is used when you are spelling a word or telling someone a number to show that a letter or digit is repeated.
the act or result of breaking; fracture [...]
twice the number, amount, size, etc [...]
You use double before a singular noun to refer to two things of the same type that occur together, or that are connected in some way.
You use double to describe a drink that is twice the normal measure.
You use double to indicate that something includes or is made of two things of the same kind.
adjective: You use double to describe something which is twice the normal size or can hold twice the normal quantity of something.
countable noun: If you refer to someone as a person's double, you mean that they look exactly like them.
predeterminer: If something is double the amount or size of another thing, it is twice as large.
uncountable noun: In tennis or badminton, when people play doubles, two teams consisting of two players on each team play against each other on the same court.
verb: If a person or thing doubles as someone or something else, they have a second job or purpose as well as their main one.
verb: When something doubles or when you double it, it becomes twice as great in number, amount, or size.